U.S. Pat. No. 3,024,037 discloses an example of a vehicular suspension system of the type described above. This vehicular suspension system includes four suspension cylinders which are provided for front left and right and rear left and right wheels of a vehicle, respectively, and which have four hydraulic chambers connected to respective four hydraulic chambers of a control cylinder. The control cylinder includes a piston assembly which consists of two pistons and a connecting rod connecting the two pistons and in which the two pistons and the connecting rod are fluid-tightly and slidably fitted in a cylinder housing. The two suspension cylinders provided for the front left and right wheels of the vehicle are connected to respective two inner hydraulic chambers which are formed between the respective two pistons and a partition wall through which the connecting rod fluid-tightly extends, while the two suspension cylinders provided for the rear left and right wheels are connected to respective two outer hydraulic chambers which are formed on axially outer sides of the respective two pistons which are remove from the connecting rod.
This vehicular suspension system is capable of preventing or restricting a pitching motion of the vehicle body such that a pitching moment acting on the vehicle body causes an equilibrium of hydraulic pressures acting on the piston assembly of the control piston in the respective opposite axial directions, so that the piston assembly is held stationary at its neutral position. In the event where one of the front left and right and rear left and right wheels runs over a raised portion of a roadway surface and moves upwardly toward the vehicle body, the piston assembly of the control cylinder is axially moved, permitting a comparatively easy upward movement of the wheel running on the raised portion, thereby effectively avoiding an undesirable motion of the vehicle body. Further, this vehicular suspension system is adjustable in its rolling rigidity on the front-wheel and rear-wheel sides, by suitably selecting a ratio of the diameter of the two pistons to the diameter of the connecting rod.